Exhaust Emissions Characterization of a Turbocharged 2-Stroke Tier 0+ Locomotive Engine: NOx, Particulate Matter and Soluble Organic Fraction Composition

Abstract

This study presents a detailed exhaust emission characterization of a 2-Stroke turbocharged line haul locomotive diesel engine fitted with an early-development Tier 0 + emissions kit. The objective of this work is to use emissions characterization to gain insight into engine operation and mechanisms of pollutant formation for this family of engine, and identify areas of potential future engine emissions improvement. Results show that at the notches tested (notches 3–8) the largest contributor to particulate matter (PM)mass is insolubles (mostly elemental carbon), but that the soluble component of PM, comprising 14–32% of PM, is also significant. Gas chromatography (GC) analysis of the soluble portion shows that it is composed of 55–77% oil-like C22–C30+ hydrocarbons, with the remainder being fuel-like C9–C21 hydrocarbons. The emissions characterization suggests that advancing combustion timing should be effective in reducing PM mass by reducing the insoluble portion (elemental carbon) of PM at all notches. NOx will likely increase, but the current level of NOx is sufficiently below Tier 0+ limits to allow a moderate increase. Reducing engine oil consumption should also reduce PM mass at all notches, although to a smaller degree than measures that reduce the insoluble portion of PM.

Comparison of Over-the-Rail and Rail Yard Measurements of Diesel Locomotives

“…Available data on locomotive emissions are typically from steady-state PME dynamometer and rail yard (RY) measurements, where exhaust emissions are measured at each notch position. − The PME is removed from the locomotive during dynamometer measurements, while the PME remains in the locomotive for rail yard measurements. The U.S. Environmental Protection Agency (EPA) locomotive emission standards for nitrogen oxides (NO x ), particulate matter (PM), carbon monoxide (CO), and hydrocarbons (HC) are based on weighted average time spent by the PME in each notch and the associated notch emission factors obtained from Federal Reference Method (FRM) measurements. ,, Few facilities in the Untied States can measure locomotive emissions using Federal Reference Methods.…”